Signals received by a radio communication device have been interfered by various signals, leading to the deterioration of the reception quality. As a technique to suppress this kind of interference and strongly receive only signals arriving from a desired direction, an adaptive array antenna (adaptive antenna) has been known. The adaptive array antenna can receive only signals arriving from a desired direction by adjusting a weight coefficient by which the receiving signals are multiplied (hereinafter, the weight coefficient is referred to as “weight”) to adjust the amplitude and phase given for receiving signals.
Furthermore, demands for the mass radio communication and high speed have been recently increased. To realize such demands, anti-multi-path property and anti-fading countermeasure have been big subjects to be solved. One of approaches to solve the subjects is multi-carrier transmission transmitting in parallel by a plurality of narrowband sub-carriers in a band for performing wideband transmission. In particular, the orthogonal frequency division multiplexing (OFDM) transmission method has been adopted in terrestrial digital broadcasting or wideband radio access systems.
When an adaptive array antenna is used in a multi-carrier transmission system, both can be further characterized, thus enhancing anti-multi-path property and anti-fading property.
Description of detailed configuration will not be described. However, in a multi-carrier transmission system, there has been described a conventional radio device equipped with an adaptive array antenna, for example, in JP-A-1999-205026. Due to this, even when the relative band (the ratio of the entire communication band in use to the center frequency of the entire communication band) was high, a directional beam of an antenna that is uniform at the entire communication bands in the OFDM transmission method can be obtained and transmission/reception that is hard to be influenced by interfering wave such as multi-path and the like in the entire communication band can be made, by calculating a weight of an antenna in the respective sub-carriers.
However, the conventional adaptive antenna radio communication device has a problem in that it was unable to estimate the direction with sufficient accuracy for receiving sub-carriers having low received power, when it was influenced by frequency selective fading for performing the direction estimation for each sub-carrier and calculating a weight of a receive array. Furthermore, it has a problem in that, when the number of sub-carriers was high, the circuit specification has increased.